Brachial Plexus Injuries Flashcards
What can cause damage to the brachial plexus?
- Injuries at birth (obstetric) - Blunt trauma - Penetrating trauma – wounds to the neck or axilla - Disease
What are injuries to the superior parts of the BP called? What nerve roots are injured?
Upper BP injury known as ‘Erb’s palsy’ C5 and C6 (sometimes C7 but not always)
What are injuries to the inferior parts of the BP called?
Lower BP injury known as ‘Klumpke’s palsy’
What happens if the whole plexus is injured?
Rarely, the whole plexus can be injured – these injuries are devastating.
What part of the BP can cervical cord injuries injure?
The roots of the BP
What part of the BP can 1st rib injuries injure?
The trunks of the BP
How does obstetric upper BP injury occur?
Occurs due to excessive stretching of the baby’s neck during delivery causing damage to C5 and C6 nerve roots
When does excessive stretching of the baby’s neck during delivery typically occur?
Usually when the baby’s shoulders are ‘stuck’ (shoulder dystocia)
What does upper BP injury lead to?
Paralysis of upper limb muscles that are supplied by C5 and C6 (and possibly C7)
What muscles are affected in upper BP injury?
Musculocutaneous nerve (C5-C7):
- Coracobrachialis
- Biceps
- Brachialis
Axillary nerve (C5 and C6):
- Deltoid
- Teres minor
Suprascapular nerve also arises from the upper trunk of the brachial plexus derived from roots C5 and C6 which innervates infraspinatus and supraspinatus
Why are motorbike accidents (or similar to this) a common cause of brachial plexus injuries?
Causes stretching of neck from shoulder due to accident –> damages brachial plexus
Here is a photograph of a baby with Erb’s palsy. Explain why the arm is positioned this way due to damage to nerves.
- Biceps and brachialis (C5, C6, C7)
- Loss of elbow flexion by both
- Loss of supination of forearm by biceps
- Teres minor and infraspinatus (C5, C6)
- Unopposed medial rotation of the shoulder as lateral rotators arren’t working
- Deltoid (axillary nerve C5, C6)
- Arm is limp by side due to loss of abductors
- Sensory deficits in C5/C6 (C7) dermatomes
What investigations are done in adult upper limb injury?
MRI: shows nerve root damage.
Where does the suprascapular nerve arise?
Arises from the superior trunk of the brachial plexus
Is obstetric lower BP injury or upper BP injury more common?
Erb’s palsy (upper BP injury) more common during delivery
What does lower BP injury lead to?
Paralysis of the UL muscles that are supplied by C8 and T1, and possibly C7.
Later in life, what can obstetric brachial plexus injuries lead to?
Poor development of muscles supplied by nerves that are injured
What causes obstetric lower BP injuries?
Excessive pulling on the baby’s upper limb during delivery causing damage to C8 and T1 nerve roots
What are adult lower BP injuries typically caused by?
Occur when excessive force is placed on an abducted shoulder and usual mechanism is that the upper limb is suddenly pulled superiorly e.g. grasping to prevent a fall
The function of which nerve will be impaired by a C8 and T1 root injury?
Ulnar nerve
What muscles does the ulnar nerve innervate in the:
- Arm?
- Forearm?
- Hand?
Arm –> none
Forearm:
- Flexor carpi ulnaris
- 1/2 digitorum profundus
Hand:
- Intrinsic muscles of the hand: hypothenar, adductor pollicis, palmaris brevis, palmar and dorsal interossei of the hand, medial two lumbricals
Which areas of skin are innervated by C8 and T1?
Medial side of hand and forearm
How can a lower BP injury affect the hand?
Can lead to paralysis of the majority of the intrinsic hand muscles
What is ‘claw hand’?
- After a lower BP injury
- An ‘imbalance’ between the ongoing function in some intrinsic & extrinsic muscles but paralysis / weakness in others leads to hand deformity
What other syndrome can a lower BP injury be associated with?
Horner’s syndrome
What are the features of Horner’s syndrome?
- Ptosis
- Miosis
- Anhidrosis
- Vasodilation
What is ptosis of the eye?
Drooping of the upper eyelid
What is miosis of the eye?
Excessive constriction of the pupil of the eye.
What is anhidrosis?
Absence of sweating
Why might a person with Klumpke’s paralysis also have Horner’s syndrome?
Sympathetic neurons supplying the head originate from T1 and may also be damaged by traction.
These neurons cause the pupil to dilate.
What is Horner’s syndrome?
Horner syndrome is a combination of signs and symptoms caused by the disruption of a nerve pathway from the brain to the face and eye on one side of the body
What are the 3 key features of Horner’s syndrome?
- decreased pupil size
- a drooping eyelid
- decreased sweating on the affected side of your face.
Where do sympathetic nerves supplying the head originate?
Thoracic region (T1-T6)
Effect of sympathetic nervous system on pupil constriction?
Causes pupil dilation
